There has been known a glass panel unit in which two or more glass panels are stacked with one or more gaps in-between to form one or more hermetically enclosed spaces, and the spaces are made to be in a vacuum state. This type of glass panel unit is referred to as a multiple glass panel. This type of glass panel unit is also referred to as a vacuum insulated glass panel. This glass panel unit has high thermal insulating properties. It is important that the glass panel unit keeps the vacuum state.
There has been proposed use of spacers to keep a thickness of the evacuated space inside the glass panel unit. The spacers are materials sandwiched between the two glass panels. The spacers are required to have strength to some extent. The spacers are frequently made of metal. In contrast, U.S. Pat. No. 6,541,084 B2 discloses spacers made of polymer. According to this technique, using polymer as material of spacers may give flexibility to the spacers. However, it is considered to be difficult to produce a glass panel unit excellent in strength by use of the spacers made of polymer.